Recently, a patent foramen ovale (hereinafter, referred as to PFO: Patent Foramen Ovale) has been cited as a cardiogenic factor in strokes and migraines. A PFO is a medical condition in which a foramen ovale which makes blood shunt for the right to the left in the heart of a baby or young child remains even after the young child becomes an adult. It is said that 20 to 30% of adults possess it.
The foramen ovale occurs at a septum secundum (Septum Secundum, hereinafter, referred to as atrial septum secundum) of the heart and the pressure on the left atrium side exceeds the pressure on the right atrium side in the heart on a normal occasion, so that it is occluded by a septum primum (Septum Primum, hereinafter, referred to as foramen ovale valve), but when the pressure on the right atrium side exceeds the pressure on the left atrium side on the occasion of a strain (for example, when coughing, when holding on) or the like, the foramen ovale valve opens to the left atrium side and it happens that blood flows from the right atrium side (venous side) into the left atrium side (arterial side). When a thrombus is included in this blood, the thrombus is shifted from the venous side to the arterial side, flows in a route of left atrium→left ventricle→aorta→brain, and becomes a factor in strokes, migraines or the like.
Treatments for such a condition include a treatment by a percutaneous catheter procedure. This is considered to be a desirable method if the same effect as an open heart surgery can be obtained.
A device of a closing technique using the percutaneous catheter can be used also in case of closing defects such as a congenital atrial septal defect indwelled (ASD), a PFO, a ventricular septal defect (VSD) and a patent ductus arteriosus (PDA). In the past, the device which has been used is a device which sandwiches the foramen ovale valve and the atrial septum secundum by using disk-shaped membranes or anchor members for closing the defect and these are indwelled in the body.
The membranes or anchor members are foreign substances for a human body and moreover, it is easy for a thrombus to be attached. In particular, when a thrombus is attached on a disk-shaped membrane or the like on the left atrium side, this flows and there is a possibility that it becomes a cause of a stroke, and there is also a fear that a foramen ovale valve of a thin wall thickness is broken. In addition, these members are not position-fixed in a state of being sandwiched and there is also a possibility of causing a positional displacement.
Consequently, recently, there has been proposed a PFO closing device which is described in WO2004/086944 A2 (see summary, FIG. 10 and the like). This PFO closing device is a device in which an apparatus is inserted into the foramen ovale from the right atrium toward the left atrium, a foramen ovale valve is pulled to the foramen ovale so as to close it and the tissue is fused by applying electric energy. However, the foramen ovale, the foramen ovale valve and the atrial septum secundum are different not only terms of sizes but also in a condition of thicknesses, shapes or the like depending on the individual and according to circumstances, the size or the like of the apparatus is restricted a lot. Also, on occasion when the procedure is performed, there is a fear that it becomes difficult to pull various forms of foramen ovale valves to the foramen ovale at anytime and certainly.
Consequently, as shown in Japanese Patent Application No. 2006-47636 (see summary, FIG. 10 and the like), the present patent applicant proposed previously a PFO closing device in which the foramen ovale valve and the atrial septum secundum are sandwiched by a pair of electrodes and the tissue is fused by applying electric energy from both the electrodes. This PFO closing device uses a clamper in which a stick portion and a sandwich member are composed of a pair of electrodes and with respect to one of them, the stick portion composed of a needle electrode is stuck into the foramen ovale valve and thereafter, the foramen ovale valve and the atrial septum secundum are sandwiched with respect to the sandwich member which is the other electrode, the biological tissue is applied with electric energy, and the fusion is carried out. If this PFO closing device is used, foreign substances are not indwelled in the body, the construction is relatively simple, also the procedure becomes relatively easy and the foramen ovale valve and the atrial septum secundum can be fused certainly.
However, in this device, the clamper is configured to be the electrodes, so that when electric energy is applied and in case of an example in which the atrial septum secundum is thick, the distance between the aimed fusion region and the electrodes is relatively far and there is a possibility that damage will occur to a region which is not intended to be fused.
Also, depending on the inter-individual difference of the thickness of a biological tissue, fluctuation occurs on the distance between the fusion region and the electrode and also there is a possibility that fluctuation will occur on the fusion force.